Endoluminal prostheses such as stents, stent-grafts and other related devices are used to treat vessels that have become weakened or diseased. These prostheses are used in a variety of circumstances to provide a remedy for the damaged vessels. The remedy can come in the form, for example, of added support for a vessel that has become weakened as a result of an aneurysm. In particular, in the case of an abdominal aortic aneurysm (AAA), in which a portion of a patient's aorta, the major artery carrying blood from the heart, has developed a weakened wall, a graft is inserted to span the weakened region to facilitate a blood flow path between the healthy portions of the aorta.
In order to reduce the risk involved with invasive abdominal surgery, in which the patient's abdominal cavity is opened so that the graft can be sutured in place, many methods of percutaneous placement have been developed. Accompanying percutaneous placement, however, is a need to maintain the graft in its inserted position in the absence of sutures. To this end, various anchoring devices have been proposed, most of which are attached to, or incorporated in, the graft. Examples of prior art anchoring devices include those found in U.S. Pat. No. 5,843,167, in the form of an assembly that is attached to the graft. The assembly includes anchors which are attached to a graft on either end and which are connected by wire struts that extend along the length of the graft. These anchors have hooks that are formed on the end of short segments of wire that are secured to the anchor. The hooks are adapted to protrude radially outwardly upon deployment of the endoprosthesis, extending a short distance beyond the bends of the anchor.
U.S. Pat. No. 5,843,164 also discloses an anchoring system that includes hooks to penetrate the aortic wall. The hooks are generally provided at each end of the stent graft, each hook having one or more barb thereon. U.S. Pat. No. 5,591,197 discloses a different type of anchor in the form of deformable connecting members that attach cylindrical elements which together form a stent. Upon balloon expansion of the connecting members, a notched, weakened area is forced outward to form a barb to penetrate the aortic wall. Finally, U.S. Pat. No. 5, 593,434 discloses a plurality of projections or teeth cut away from a sheet of material, which is curled into a cylinder to form a stent.
The drawback to these and other anchoring systems is that the teeth or hooks attached or integrated into the grafts or stents have a tendency to catch on the delivery sheaths or catheters during deployment. This creates problematic situations in the deployment process as the teeth or hooks tear the sheath material, preventing the necessary precision required in percutaneous delivery into a body lumen.
Thus, it would be desirable to provide an anchoring device for an endoluminal prosthesis, which will forcefully engage the vessel wall upon deployment and be configured so that contact with the delivery sheath or catheter upon insertion of the prosthesis is avoided.